WSP Opus Research looked into the impact of noise from roading projects on community satisfaction
A paradox of New Zealand life is that while there is almost a car for every adult member of the population, we appear to be averse to the noise of other people using cars.
Road traffic noise is one of the most frequently raised concerns about roading projects, and the management of road traffic noise is now a top priority. We regularly undertake noise assessments for roading projects, applying the guidelines and standards relating to acceptable noise levels, as determined by stakeholders.
Gauging acceptable noise limits
In addition to noise assessments, we also undertake research into topics relating to road traffic noise. In one research project for the New Zealand Transport Agency, we investigated how communities live with road traffic noise, and in particular what the community regards as acceptable road traffic noise.
In this project, four roading projects from across New Zealand were studied and residents from over 130 properties surveyed. Two of these projects were major roads constructed with noise mitigation to achieve the lowest practicable noise level, while the other two projects involved major roads constructed to achieve medium noise levels. The survey asked respondents to rate their satisfaction, neutrality or dissatisfaction with twelve attributes of their neighbourhood including condition of roads and footpaths, rubbish collection, neighbourhood crime, parks, trees in the area, noise from neighbours and animals, and vehicle noise.
As people tend to like where they live, it was no surprise that responses were very highly and positively skewed for nearly all of the neighbourhood attributes. The exceptions were road traffic noise and vehicle speeds. It was significant to observe that even in the same noise ‘environment’, many residents were satisfied or very satisfied with road traffic noise levels as well as there being many residents who were dissatisfied or highly dissatisfied.
Unsurprisingly, in the medium noise environment, there were more residents who were dissatisfied or highly dissatisfied than in the lowest noise environment.
To get a benchmark for ‘reasonable’ noise, we also looked at residents’ reactions to noise such as increasing the volume on their television or shutting their windows. This quantification approach is found to provide a more objective measure of ‘noise disturbance’ rather than more subjective responses to noise such as the degree of annoyance. The survey found that residents who took action to reduce noise disturbance did so most often when the traffic was busiest or during the night.
Three key findings
Overall these findings highlight three important aspects of road traffic noise management:
- The community response is broad even within the same noise environment
- Road traffic noise should be managed according to the typical response of the community, and not the individual
- It is usually not possible to achieve noise levels that will satisfy everyone
- Nevertheless where practicable, steps can be taken in road design to decrease road traffic noise, and as a result community satisfaction with their noise environment should improve